Two really good software utilities to have on your computer are Malwarebytes (http://www.malwarebytes.org) and CCleaner (http://www.piriform.com). Both software applications are available for Windows and Mac and come in free and paid versions.
Malwarebytes is a good utility to detect and remove malware on your computer especially malware that is not typically detected by traditional antivirus software. Malwarebytes can help to compliment and supplement your antivirus software. While many software manufacturers do offer a variety of comprehensive utilities, these packages may be difficult to manage & configure and be significantly more expensive. Malwarebytes is fairly simple to use, does not require significant configuration and is effective. While the free version does not offer real-time scanning protection, it is still quite effective when run periodically as part of a preventive maintenance routine.
CCleaner by Piriform is a good utility to help keep your computer clean and free up space consumed by temporary files. Web browsers tend to keep cached temporary files for a significant period of time if you do not custom configure the settings to automatically delete the cache, temporary files and browsing history associated with those browsers or manually purge those files periodically. Application installations may store temporary files in a variety of temp folders on your computer which can consume a substantial amount of storage space and web downloads can also do the same. CCleaner will search designated temporary folders and locations and provide a list of files which can be purged. Before purging the files, you will have an opportunity to review those files before choosing to remove those files. CCleaner can also help purge registry files (Windows) that are no longer required by the OS, provides an optimization tool to optimize your hard disk (Windows, non-SSDs) and offers up a selection of other useful maintenance tools. CCleaner is another useful tool to keep and use as part of your preventive maintenance routine.
Both Malwarebytes and CCleaner receive periodic software updates so make sure the notifications are enabled and/or you periodically check for the latest software updates.
If you are not comfortable or familiar with performing maintenance tasks or using these software utilities on your computer, consult with an experienced IT professional.